Advanced Engineering Forum Vol. 34

Abstract: Additive manufacturing [AM] is a type of production technology characterized by the additive nature of stacking and unifying individual layers, with the main advantage that parts with complex geometries can easily be obtained, compared to conventional production methods. Due to its working principle, i.e. stacking layers, obtained by melting and solidification, the mechanical characteristics of the built part might be influenced by the build orientation chosen for the specific part. The mechanical behavior, cyclic deformation and fatigue behaviors of additively manufactured metallic parts as compared to their counterparts obtained by conventional processing technologies was reported to be highly dependent on the build orientation. The aim of this study was to assess whether the build orientation will have an impact on the mechanical properties of parts built by Selective Laser Sintering, using polyamide powder as raw material. Samples were built at various inclination degrees, and were further tested in terms of bending, compressive, impact and hardness tests. It was observed that the build orientation has a significant effect on the mechanical properties of parts additively manufactured from polyamide, compared to the behavior presented on the technical sheet of the material, provided by the manufacturer. Keywords: additive manufacturing, mechanical properties, build orientation, Selective Laser Sintering

Abstract: Usage of electron beam shows the possibility of using its energy in different thermic processes. Among these, it is found the heating of mechanical products for the surface heat treatment. During the effectuated practical attempts, two types of construction steels were analyzed, namely carbon steel (OLC 45) and a low alloyed steel (41 Cr 4). The electron beam was applied on samples that were previous subjected to the heat treatment of improvement. The working parameters were chosen in order to obtain the heating of the superficial layer without melting. The samples treated as above were subjected to studies regarding the metallographic structures and the resulted hardness; also there were effectuated wear attempts. It was concluded that the use of electron beam in superficial heat treatment may also fit in practical terms.

Abstract: In the automotive industry there is a clear trend towards alternative drivetrain systems, away from the classical internal combustion – gasoline or diesel - engines. This poses a challenge to the traditional markets of powder metallurgy, the ferrous precision parts for automotive engines and transmissions which form the major tonnage of today’s powder metallurgy [1, 2], but also the hardmetal tools for machining automotive components from stock material or for finishing [3]. To counter these trends, powder metallurgy can rely on its high flexibility regarding materials, geometries, processing and properties and finally applications, which enables PM to adapt itself to changing requirements in a changing industrial environment [4]. In the present article, examples are given both for PM precision parts and hardmetals but also functional materials such as soft magnetic composites. It is shown that the potential of ferrous PM parts regarding mechanical performance is still higher than currently used, high and graded density being attractive ways [5]. Also the use of advanced alloying systems offers economical and technical advantages and should enable PM to enter non-automotive markets for precision parts. In the hardmetal branch, non-automotive applications, e.g. in construction and mining, should be considered while from the material viewpoint replacing tungsten and in particular Co as binder metal are intensely studied. PM functional materials such as Fe-Ni, Fe-Co and in particular soft magnetic composites will find markets in electrical drive systems [6], enabling new designs for electric motors. On the other end of the spectrum, superhard rare earth magnets are regularly produced by the powder route. Finally, the multitude of additive manufacturing techniques offers chances for powder metallurgy since most of these processes start from metal powders [7]. In addition to the well known laser and electron beam based “direct” AM systems, also indirect, binder-based, variants are attractive, avoiding many problems encountered with the direct systems and enabling transfer of knowhow accumulated in metal injection moulding. In general, future will show how many other technologies and products has to offer in addition to the classical press-and-sinter routes which however will remain for their specific product groups. when designing your figures and tables, etc

Abstract: The main purpose of this paper is to analyze the temperature in turning process of a titanium bar, both with noncontact infrared thermometer and thermocouple. In order to have a comparative appreciation of the difference between the temperature measured with contact and noncontact methods, the determinations are graphically represent separately and on the same figure.

Abstract: In this paper, the authors present the influence of cutting parameters, depth of cut, rotational speed and speed feed on the process temperature for milling of three types of aluminum alloys. In order to measure the temperature, an adequate experimental setup was used. This experimental setup consists in a noncontact infrared thermometer.

Abstract: The surface roughness of tool edge and surface can affect the friction, between the rake face and chips and also the cutting force and temperature. For this reasons, in order to assure a good quality, some experimental determinations, from point of view of rake face roughness, are presented in this paper. The results, as capture from a SEM microscope, and, graphically dependencies of roughness as function of process parameters, are presented.

Abstract: In this paper, BaFe₂O₄ was prepared from BaCO₃ and Fe₂O₃ powders through the solid state reaction method. This method starts by mixing the barium carbonate and iron oxide in order to homogenize the raw materials and takes place in a wet medium. For a better homogenization of BaCO₃ and Fe₂O₃ powders and in order to reduce the monoferrite formation temperature, it was used the mechanical alloying process for 3 and 9 hours in a high energy ball mill. Particle size distributions of the milled powders were analyzed by a BROOKHAVEN 90PLUS device. To understand the phase formation temperature, thermogravimetry analysis was carried out. The phase identification of the calcined powder was carried out by D8 Discover Bruker X-ray diffractometer. The results showed that once with the reduction of powders particle size, in the mechanical alloying process, the temperature of the solid state reaction of barium monoferrite was also reduced.

Abstract: The paper is focused on the elaboration of some sintered steels with Cr concentration between (1-2 %) wt., carbon as graphite with a concentration of 0,4% wt. and Fe for the balance. The samples were die pressed at 600 MPa and sintered at 1150 °C in argon atmosphere. The samples were studied from the point of view of wear behavior against three types of counter balls, alumina (Al₂O₃), steel (100Cr6) and stainless steel 440C. The results shows that the lowest value for the friction coefficient was attained for the steel with 1,5% Cr. Also, microhardness tests were performed and reveal that the highest value was equal to 229 HV_05.

Abstract: In the paper is presented the analysis of tool steel used for making a knife for a mill for grinding plants. The material used for the knife is about 1% carbon and is symbolized by RWL34. To improve the properties of the material, especially the knife cut, a thermal treatment were made and was measured hardness, wear resistance and microscopic analyzes of the metal. The paper presents the values of the mechanical properties on the initial sample, on the hardening sample and on the sample subjected to a hardening and tempering treatment, as well as the graphs related to them. The next step in finalizing the analysis of the grinder mill knife is to study the behavior in operation and the possible corrections that should be made.